From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Olof Johansson <olof@austin.ibm.com>,
Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@osdl.org>,
jamie@shareable.org, Rusty Russell <rusty@rustcorp.com.au>,
David Howells <dhowells@redhat.com>
Subject: Re: [PATCH/RFC] Futex mmap_sem deadlock
Date: Wed, 23 Feb 2005 08:42:12 +1100 [thread overview]
Message-ID: <1109108532.5411.149.camel@gaston> (raw)
In-Reply-To: <Pine.LNX.4.58.0502221330360.2378@ppc970.osdl.org>
On Tue, 2005-02-22 at 13:31 -0800, Linus Torvalds wrote:
>
> On Wed, 23 Feb 2005, Benjamin Herrenschmidt wrote:
> >
> > Isn't Olof scheme racy ? Can't the stuff get swapped out between the
> > first get_user() and the "real" one ?
>
> Yes. But see my suggested modification (which I still think is "the thing
> that Olof does", except it's more efficient and avoids the race).
>
> If rwsems acted like rwlocks, we wouldn't have this issue at all.
Yours is probably the most efficient too. Note sure what is best for
rwsems tho, there seem to be some interest preventing readers from
starving writers for ever, this has been debated endlessly iirc,
though I have no personal opinion there.
Ben.
next prev parent reply other threads:[~2005-02-22 21:43 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-02-22 19:06 [PATCH/RFC] Futex mmap_sem deadlock Olof Johansson
2005-02-22 19:36 ` Linus Torvalds
2005-02-22 21:16 ` Benjamin Herrenschmidt
2005-02-22 21:19 ` Benjamin Herrenschmidt
2005-02-22 21:31 ` Linus Torvalds
2005-02-22 21:42 ` Benjamin Herrenschmidt [this message]
2005-02-22 22:10 ` Linus Torvalds
2005-02-22 22:24 ` Benjamin Herrenschmidt
2005-02-22 23:08 ` Greg KH
2005-02-23 11:24 ` David Howells
2005-02-22 19:55 ` Andrew Morton
2005-02-22 21:07 ` Jamie Lokier
2005-02-22 21:19 ` Olof Johansson
2005-02-22 22:09 ` Jamie Lokier
2005-02-22 21:19 ` Chris Friesen
2005-02-22 21:27 ` Jamie Lokier
2005-02-22 21:30 ` Linus Torvalds
2005-02-22 22:34 ` Jamie Lokier
2005-02-22 22:42 ` Olof Johansson
2005-02-22 23:20 ` Andrew Morton
2005-02-22 23:23 ` Olof Johansson
2005-02-23 11:39 ` David Howells
2005-02-23 16:22 ` Olof Johansson
2005-02-23 18:44 ` David Howells
2005-02-23 14:49 ` Joe Korty
2005-02-23 15:54 ` Linus Torvalds
2005-02-23 17:10 ` Olof Johansson
2005-02-23 17:37 ` Arjan van de Ven
2005-02-23 18:22 ` Jamie Lokier
2005-02-23 18:34 ` Linus Torvalds
2005-02-23 18:49 ` Jamie Lokier
2005-02-23 19:12 ` Olof Johansson
2005-02-23 22:00 ` Linus Torvalds
2005-02-24 0:00 ` Jamie Lokier
2005-02-23 18:37 ` Olof Johansson
2005-02-22 21:40 ` Andrew Morton
2005-02-22 21:59 ` Linus Torvalds
2005-02-23 11:42 ` David Howells
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